The present invention relates to a metal matrix powder for use along with an infiltrant to form a metal matrix. More particularly, the invention pertains to a metal matrix powder for use along with an infiltrant to form a metal matrix wherein the metal matrix exhibits improved abrasion resistance properties and/or improved strength properties.
Heretofore, a hard composite has been formed by positioning one or more hard elements (or members) within a metal matrix powder, and then infiltrating the metal powder matrix with an infiltrant metal to form the metal matrix with the hard elements held therein. This hard composite can be useful as a cutter or a wear member. More particularly, the hard composite can be a diamond composite that comprises a metal matrix (i.e., metal matrix powder infiltrated and bonded together by an infiltrant metal) with one or more discrete diamond-based elements held therein. These diamond-based elements could comprise a discrete-diamond composite or polycrystalline diamond composite having a substrate with a layer of polycrystalline diamond thereon. The following patents pertain to an infiltrant matrix powder: U.S. Pat. No. 5,589,268 to Kelley et al., U.S. Pat. No. 5,733,649 to Kelley et al., U.S. Pat. No. 5,733,664 to Kelley et al., and each one of these patents is assigned to Kennametal Inc.,
Typical metal matrix powders have included macrocrystalline tungsten carbide as a significant component. Macrocrystalline tungsten carbide is essentially stoichiometric WC which is, for the most part, in the form of single crystals. Some large crystals of macrocrystalline tungsten carbide are bicrystals. U.S. Pat. No. 3,379,503 to McKenna for a PROCESS FOR PREPARING TUNGSTEN MONOCARBIDE, assigned to the assignee of the present patent application, discloses a method of making macrocrystalline tungsten carbide. U.S. Pat. No. 4,834,963 to Terry et al. for MACROCRYSTALLINE TUNGSTEN MONOCARBIDE POWDER AND PROCESS FOR PRODUCING, assigned to the assignee of the present patent application, also discloses a method of making macrocrystalline tungsten carbide.
Metal matrix powders have also included crushed cemented tungsten carbide. This material comprises small particles of tungsten carbide bonded together in a metal matrix. As one example, the crushed cemented macrocrystalline tungsten carbide with a binder (cobalt) is made by mixing together WC particles, Co powder and a lubricant. This mixture is pelletized, sintered, cooled, and then crushed. The pelletization does not use pressure, but instead, during the mixing of the WC particles and cobalt, the blades of the mixer cause the mixture of WC and cobalt to ball up into pellets.
Metal matrix powders have also used crushed cast tungsten carbide. Crushed cast tungsten carbide forms two carbides; namely, WC and W2C. There can be a continuous range of compositions therebetween. An eutectic mixture is about 4.5 weight percent carbon. Cast tungsten carbide commercially used as a matrix powder typically has a hypoeutectic carbon content of about 4 weight percent. Cast tungsten carbide is typically frozen from the molten state and comminuted to the desired particle size.
While these earlier metal matrices for a hard composite have performed in a satisfactory fashion, it would be desirable to provide an improved matrix for a hard composite having improved properties. These properties include impact strength, transverse rupture strength, hardness, abrasion resistance, and erosion resistance. It would also be desirable to provide an improved hard composite that uses the improved matrix material